Real-time control of reductant droplet spray momentum and in-exhaust spray distribution

ABSTRACT

A system for controlling reductant spray momentum for a target spray distribution includes an exhaust system having an exhaust conduit with exhaust flowing therethrough, a reductant injection system for injecting reductant into the exhaust flowing through the exhaust system based on one or more injection parameters, a reductant supply system for supplying reductant to the reductant injection system based on one or more supply parameters, and a controller. The controller is configured to access current vehicle, engine, exhaust, or reductant condition parameters, determine one or more control parameters based on a control model and the accessed current vehicle, engine, exhaust, or reductant condition parameters, and modify a value of the one or more injection parameters or the one or more supply parameters to control the reductant spray.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalPatent Application No. 62/431,092, filed Dec. 7, 2016 and entitled“REAL-TIME CONTROL OF REDUCTANT DROPLET SPRAY MOMENTUM AND IN-EXHAUSTSPRAY DISTRIBUTION,” the entire disclosure of which is incorporatedherein by reference.

TECHNICAL FIELD

The present application relates generally to the field of aftertreatmentsystems for internal combustion engines.

BACKGROUND

For internal combustion engines, such as diesel engines, nitrogen oxide(NO_(x)) compounds may be emitted in the exhaust. To reduce NO_(x)emissions, a SCR process may be implemented to convert the NO_(x)compounds into more neutral compounds, such as diatomic nitrogen, water,or carbon dioxide, with the aid of a catalyst and a reductant. Thecatalyst may be included in a catalyst chamber of an exhaust system,such as that of a vehicle or power generation unit. A reductant such asanhydrous ammonia or urea is typically introduced into the exhaust gasflow prior to the catalyst chamber. To introduce the reductant into theexhaust gas flow for the selective catalytic reduction (SCR) process, anSCR system may dose, inject, or otherwise introduce the reductantthrough a doser that vaporizes, injects, or sprays the reductant into anexhaust pipe of the exhaust system up-stream of the catalyst chamber.The SCR system may include one or more sensors to monitor conditionswithin the exhaust system.

SUMMARY

Implementations described herein relate to systems and methods forcontrolling reductant spray for a target spray distribution based onmodifying one or more parameters of a reductant injection system orreductant supply system in real-time using current vehicle, engine,exhaust, and/or reductant condition parameters.

One implementation relates to a system for controlling reductant spraymomentum for a target spray distribution comprising an exhaust systemhaving an exhaust conduit with exhaust flowing therethrough, a reductantinjection system for injecting reductant into the exhaust flowingthrough the exhaust system based on one or more injection parameters, areductant supply system for supplying reductant to the reductantinjection system based on one or more supply parameters, and acontroller. The controller is configured to access current vehiclecondition parameters, engine condition parameters, exhaust conditionparameters or reductant condition parameters, determine one or morecontrol parameters based on a control model and the accessed currentvehicle condition parameters, engine condition parameters, exhaustcondition parameters or reductant condition parameters, and modify avalue of the one or more injection parameters or the one or more supplyparameters to control a reductant spray momentum, a reductant dropletmomentum, a reductant spray momentum, or a reductant momentum vectorfrom the reductant injection system for a target spray dropletdistribution or a target spray distribution.

In some implementations, the current exhaust condition parameterscomprise at least one of an exhaust temperature, an exhaust flowvelocity, an exhaust mass flow, or an exhaust vorticity. In someimplementations, the current reductant condition parameters include atleast one of a reductant temperature, reductant supply pressure,required injection momentum based on exhaust or liquid reductantconditions, a reductant density, an injection frequency, or a nozzlegeometry. In some implementations, the control model is an empiricalmodel. A Latin hypercube study may be performed to compute parameters ofthe empirical model for an exhaust system platform using a range ofvalues for exhaust properties and reductant properties. In someimplementations, the control model is a physics based model. Parametersof the physics based model may be obtained by performing a Latinhypercube study for an exhaust system platform using a range of valuesfor exhaust properties and reductant properties. In someimplementations, the current vehicle condition parameters can include atleast one of a vehicle speed, a vehicle tire pressure, a vehicleinclination angle, a vehicle drive gear selection, a vehicle mass, avehicle weight, a vehicle trailer weight, or a vehicle air linepressure. In some implementations, the current engine conditionparameters can include at least one of an engine fuel flow rate, anengine air flow rate, an engine boost pressure, an engine intakepressure, an engine load, an engine rotational speed, an engine cylindertemperature, an engine cylinder pressure, or an engine fuel pressure. Insome implementations, the controller can use the current vehiclecondition parameters, engine condition parameters, exhaust conditionparameters or reductant condition parameters to determine the reductantspray momentum and modifies one or more injection parameters to achievea target spray droplet distribution or a target spray distribution forthe current vehicle condition parameters, engine condition parameters,exhaust condition parameters or reductant condition parameters.

Another implementation relates to a method that includes accessingcurrent vehicle condition parameters, engine condition parameters,exhaust condition parameters or reductant condition parameters;determining one or more control parameters based on a control model andthe accessed current vehicle condition parameters, engine conditionparameters, exhaust condition parameters or reductant conditionparameters; modifying a value of an injection parameter or a supplyparameter to control a reductant spray momentum, a reductant dropletmomentum, a reductant spray momentum, or a reductant momentum vectorfrom a reductant injection system for a target spray dropletdistribution or a target spray distribution; and commanding a reductantinjection system to inject reductant into an exhaust based on theinjection parameter or a reductant supply system to supply reductant tothe reductant injection system based on the supply parameter.

In some implementations, the current exhaust condition parameters caninclude at least one of an exhaust pressure, an exhaust density, anexhaust temperature, an exhaust flow velocity, an exhaust mass flow, oran exhaust vorticity. The current reductant condition parameters caninclude at least one of a reductant temperature, reductant momentumbased on an injection supply pressure, a reductant density, an injectionfrequency, a reductant air supply pressure, a reductant air supply flowrate, a reductant spray cone angle, or a nozzle geometry. The currentvehicle condition parameters can include at least one of a vehiclespeed, a vehicle tire pressure, a vehicle inclination angle, a vehicledrive gear selection, a vehicle mass, a vehicle weight, a vehicletrailer weight, or a vehicle air line pressure. The current enginecondition parameters comprise at least one of an engine fuel flow rate,an engine air flow rate, an engine boost pressure, an engine intakepressure, an engine load, an engine rotational speed, an engine cylindertemperature, an engine cylinder pressure, or an engine fuel pressure.The current vehicle condition parameters, engine condition parameters,exhaust condition parameters or reductant condition parameters can beused to determine the reductant spray momentum and modify the injectionparameter to achieve a target spray droplet distribution or a targetspray distribution for the current vehicle condition parameters, enginecondition parameters, exhaust condition parameters or reductantcondition parameters.

Still another implementation relates to a system that includes areductant injection system for injecting reductant into an exhaust basedon an injection parameter or a supply parameter and a controller. Thecontroller is configured to access current exhaust condition parametersor reductant condition parameters, determine one or more controlparameters based on a control model and the accessed current exhaustcondition parameters or reductant condition parameters, and modify avalue of the injection parameter or the supply parameter to control areductant spray momentum, a reductant droplet momentum, a reductantspray momentum, or a reductant momentum vector from the reductantinjection system for a target spray droplet distribution or a targetspray distribution.

In some implementations, the current exhaust condition parameterscomprise at least one of an exhaust temperature, an exhaust flowvelocity, an exhaust mass flow, or an exhaust vorticity. In someimplementations, the current reductant condition parameters include atleast one of a reductant temperature, reductant supply pressure,required injection momentum based on exhaust or liquid reductantconditions, a reductant density, an injection frequency, or a nozzlegeometry. In some implementations, the control model is based on a Latinhypercube study performed to compute parameters of the empirical modelfor an exhaust system platform using a range of values for exhaustproperties and reductant properties.

BRIEF DESCRIPTION

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features,aspects, and advantages of the disclosure will become apparent from thedescription, the drawings, and the claims, in which:

FIG. 1 is a block schematic diagram of an example selective catalyticreduction system having an example reductant delivery system for anexhaust system;

FIG. 2 is a graphical diagram depicting droplet paths in an exhaustvector field with a droplet distribution graph for a system with nodroplet control;

FIG. 3 is a graphical diagram of a distribution of droplet diameters asa function of injection pressure;

FIG. 4 is a set of graphical diagrams of particle flight paths ofdroplets of different diameters at the same injection velocity in anexhaust pipe having a uniform flow velocity field;

FIG. 5 is a set of graphical diagrams of particle flight paths ofdroplets having the same diameter at different injection velocities ormomentums in an exhaust pipe having a uniform flow velocity field;

FIG. 6 is a graphical diagram depicting droplet paths in an exhaustvector field with a droplet distribution graph for a system with dropletcontrol;

FIG. 7 is a process diagram for developing a control model for dropletcontrol in an exhaust system; and

FIG. 8 is a process diagram for implementing the control model fordroplet control in an exhaust system.

It will be recognized that some or all of the figures are schematicrepresentations for purposes of illustration. The figures are providedfor the purpose of illustrating one or more implementations with theexplicit understanding that they will not be used to limit the scope orthe meaning of the claims.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and implementations of, methods, apparatuses, and systemsfor real-time control of injection of reductant. The various conceptsintroduced above and discussed in greater detail below may beimplemented in any of numerous ways, as the described concepts are notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

I. Overview

In some exhaust aftertreatment systems, the reductant injection systemoperates with a singular droplet momentum regardless of environmental,e.g. exhaust, conditions. This can lead to an uncontrolled in-exhaustspray distribution and spatial placement (i.e., an uneven amount ofreductant in the cross-sectional area of the exhaust stream) atdifferent exhaust conditions. The effectiveness of injected reductantmay be affected by several factors, such as a reductant spray quality,droplet diameter (i.e., droplet mass), droplet velocity, droplettrajectory, cone angle, spray in-exhaust distribution, momentum, spraypenetration length, final distribution of the decomposed reductant inthe exhaust stream, etc. Two controllable characteristics that affectreductant droplet momentum and in-exhaust distribution are dropletdiameter and droplet velocity. Nozzle design and supply pressure bothcan impact the droplet diameter and droplet velocity, and thus affectthe droplet momentum. If the diameter and velocity of the reductantdroplets are both large values, then, at low exhaust flow velocities,the droplets can penetrate into the exhaust stream too deeply, impactingwalls and creating deposits while decreasing NO_(x) reductionefficiency. If the diameter and velocity of the reductant droplets aresmall values, then, at higher exhaust flow velocities, these dropletstend to ‘hug’ the exhaust piping walls adjacent to the injectorlocation, thereby limiting the NO_(x) reduction efficiency. Similarly, alarge single dose of reductant may be less effective due to the exhausttemperature being unable to sufficiently decompose the reductant priorto a catalyst, while multiple smaller doses of reductant can be moreefficiently decomposed by the available exhaust heat energy.Accordingly, providing a system that varies the droplet placement basedon droplet momentum and injection timing (i.e., number of doses per unittime) according to engine operation conditions may be useful to improvein-exhaust spray distribution and NO_(x) reduction efficiency.

In some implementations, a real-time reductant delivery system canmodify an injection supply pressure, injection frequency, and/or dosernozzle geometry to control the reductant spray momentum based on sensedexhaust and/or liquid reductant conditions, such as exhaust pressure,exhaust density, exhaust temperature, exhaust flow velocity, reductanttemperature, reductant velocity based on injection supply pressure,reductant density, etc. Such modification of the reductant spray inreal-time can enhance the reductant delivery system's performance androbustness. In particular, by modifying the reductant spray momentum,the in-exhaust spray distribution may be improved, thereby increasingNO_(x) reduction efficiency, and reductant deposits may be reduced.

A reductant delivery system can include hardware, software, electronic,and hydraulic components used to deliver reductant to diesel exhaustgas. A reductant delivery system can be broken down into two subsystems,a reductant supply system and a reductant injection system. Thereductant supply system can include a reductant tank storing reductant,a pump, and hydraulic tubing for delivering the reductant from thereductant tank to the pump and to a reductant delivery system. Thereductant delivery system can include an injector or doser. In someimplementations the reductant delivery system may be a liquid onlysystem that utilizes the pressure from the pump to spray reductant intothe exhaust system. In other implementations, the reductant deliverysystem may be an air-assisted system that includes an air supply sourceand hydraulic tubing to deliver the air to the reductant injector ordoser, upstream of the injector or doser, and/or at the point ofreductant injection, to assist in spraying the reductant into theexhaust system.

In some implementations, the control of the reductant spray may bethrough physical mechanisms and/or software control of the components ofthe reductant delivery system. For instance, the reductant injectionsupply pressure may be based on a change to a pump speed command, amovement of an electromechanical valve, a modification of a signal orcommand for reductant injection frequency, a modification to a dosernozzle geometry, etc. In some instances, the reductant injection supplypressure may also be modified to control the droplet breakup to controlthe droplet diameter and spray geometry for a desired spray penetrationand/or dispersion in the exhaust pipe cross-section. In someimplementations, the injection frequency may be modified to control heattransfer inside the pipe at impingement locations as well as spraygeometry due to spray development schedule (i.e., how long it takes aspray to materialize to fully developed flow) inside the pipe.

By controlling the injection supply pressure and/or injection frequency,the spray geometry and penetration can be controlled to supply both awell dispersed reductant cloud, as well as a well-placed reductant cloudthat both increases distribution and decreases wall impingement, whichforms urea deposits, based on engine operating conditions. Thus,real-time targeted spray characteristics can be adjusted duringtransient engine operation as variation in flow, temperature, or otherexhaust conditions affect reductant droplet placement and NO_(x)reduction performance and deposit generation.

II. Overview of Aftertreatment System

FIG. 1 depicts an aftertreatment system 100 having an example reductantdelivery system 110 for an exhaust system 190. The aftertreatment system100 includes a particulate filter, for example a diesel particulatefilter (DPF) 102, the reductant delivery system 110, a reactor pipe ordecomposition chamber 104, a SCR catalyst 106, and a sensor 150.

The DPF 102 is configured to remove particulate matter, such as soot,from exhaust gas flowing in the exhaust system 190. The DPF 102 includesan inlet, where the exhaust gas is received, and an outlet, where theexhaust gas exits after having particulate matter substantially filteredfrom the exhaust gas and/or converting the particulate matter intocarbon dioxide.

The decomposition chamber 104 is configured to convert a reductant, suchas urea, aqueous ammonia, or diesel exhaust fluid (DEF), into ammonia.The decomposition chamber 104 includes a reductant delivery system 110having a doser 112 configured to dose the reductant into thedecomposition chamber 104. In some implementations, the reductant isinjected or otherwise inserted upstream of the SCR catalyst 106. Thereductant droplets then undergo the processes of evaporation,thermolysis, and hydrolysis to form gaseous ammonia within the exhaustsystem 190. The decomposition chamber 104 includes an inlet in fluidcommunication with the DPF 102 to receive the exhaust gas containingNO_(x) emissions and an outlet for the exhaust gas, NO_(x) emissions,ammonia, and/or remaining reductant to flow to the SCR catalyst 106.

The decomposition chamber 104 includes the doser 112 mounted to thedecomposition chamber 104 such that the doser 112 may dose the reductantinto the exhaust gases flowing in the exhaust system 190. The doser 112may include an insulator 114 interposed between a portion of the doser112 and the portion of the decomposition chamber 104 to which the doser112 is mounted. The doser 112 is fluidly coupled to one or morereductant sources 116. In some implementations, a pump 118 may be usedto pressurize the reductant from the reductant source 116 for deliveryto the doser 112.

The doser 112 and pump 118 are also electrically or communicativelycoupled to a controller 120. The controller 120 is configured to controlthe doser 112 to dose reductant into the decomposition chamber 104. Thecontroller 120 may also be configured to control the pump 118. Thecontroller 120 may include a microprocessor, an application-specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), etc.,or combinations thereof. The controller 120 may include memory which mayinclude, but is not limited to, electronic, optical, magnetic, or anyother storage or transmission device capable of providing a processor,ASIC, FPGA, etc. with program instructions. The memory may include amemory chip, Electrically Erasable Programmable Read-Only Memory(EEPROM), erasable programmable read only memory (EPROM), flash memory,or any other suitable memory from which the controller 120 can readinstructions. The instructions may include code from any suitableprogramming language.

In certain implementations, the controller 120 is structured to performcertain operations, such as those described herein in relation to FIGS.7-8 . In certain implementations, the controller 120 forms a portion ofa processing subsystem including one or more computing devices havingmemory, processing, and communication hardware. The controller 120 maybe a single device or a distributed device, and the functions of thecontroller 120 may be performed by hardware and/or as computerinstructions on a non-transient computer readable storage medium.

In certain implementations, the controller 120 includes one or moremodules structured to functionally execute the operations of thecontroller 120. In certain implementations, the controller 120 mayinclude a control model module and/or dosing control module forperforming the operations described in reference to FIGS. 7-8 . Thedescription herein including modules emphasizes the structuralindependence of the aspects of the controller 120 and illustrates onegrouping of operations and responsibilities of the controller 120. Othergroupings that execute similar overall operations are understood withinthe scope of the present application. Modules may be implemented inhardware and/or as computer instructions on a non-transient computerreadable storage medium, and modules may be distributed across varioushardware or computer based components. More specific descriptions ofcertain embodiments of controller operations are included in the sectionreferencing FIGS. 7-8 .

Example and non-limiting module implementation elements include sensorsproviding any value determined herein, sensors providing any value thatis a precursor to a value determined herein, datalink and/or networkhardware including communication chips, oscillating crystals,communication links, cables, twisted pair wiring, coaxial wiring,shielded wiring, transmitters, receivers, and/or transceivers, logiccircuits, hard-wired logic circuits, reconfigurable logic circuits in aparticular non-transient state configured according to the modulespecification, any actuator including at least an electrical, hydraulic,or pneumatic actuator, a solenoid, an op-amp, analog control elements(springs, filters, integrators, adders, dividers, gain elements), and/ordigital control elements.

The SCR catalyst 106 is configured to assist in the reduction of NO_(x)emissions by accelerating a NO_(x) reduction process between the ammoniaand the NO_(x) of the exhaust gas into diatomic nitrogen, water, and/orcarbon dioxide. The SCR catalyst 106 includes an inlet in fluidcommunication with the decomposition chamber 104 from which exhaust gasand reductant is received and an outlet in fluid communication with anend of the exhaust system 190.

The exhaust system 190 may further include an oxidation catalyst, forexample a diesel oxidation catalyst (DOC), in fluid communication withthe exhaust system 190 (e.g., downstream of the SCR catalyst 106 orupstream of the DPF 102) to oxidize hydrocarbons and carbon monoxide inthe exhaust gas.

In some implementations, the DPF 102 may be positioned downstream of thedecomposition chamber or reactor pipe 104. For instance, the DPF 102 andthe SCR catalyst 106 may be combined into a single unit, such as a DPFwith SCR-coating (SDPF). In some implementations, the doser 112 mayinstead be positioned downstream of a turbocharger or upstream of aturbocharger.

The sensor 150 may be coupled to the exhaust system 190 to detect acondition of the exhaust gas flowing through the exhaust system 190. Insome implementations, the sensor 150 may have a portion disposed withinthe exhaust system 190, such as a tip of the sensor 150 may extend intoa portion of the exhaust system 190. In other implementations, thesensor 150 may receive exhaust gas through another conduit, such as asample pipe extending from the exhaust system 190. While the sensor 150is depicted as positioned downstream of the SCR catalyst 106, it shouldbe understood that the sensor 150 may be positioned at any otherposition of the exhaust system 190, including upstream of the DPF 102,within the DPF 102, between the DPF 102 and the decomposition chamber104, within the decomposition chamber 104, between the decompositionchamber 104 and the SCR catalyst 106, within the SCR catalyst 106, ordownstream of the SCR catalyst 106. In addition, two or more sensor 150may be utilized for detecting a condition of the exhaust gas, such astwo, three, four, five, or size sensor 150 with each sensor 150 locatedat one of the foregoing positions of the exhaust system 190.

III. Real-Time Control of Reductant Droplet Spray Momentum andIn-Exhaust Distribution

Real-time or substantially real-time control of the reductant spraymomentum and/or the in-exhaust distribution through control of thereductant droplet diameter and velocity may improve the NO_(x) reductionefficiency of the exhaust aftertreatment system. That is, by improvingthe in-exhaust distribution proximate to the reductant injection point,the mixing of reductant and NO_(x) present in the exhaust gas can occurfurther upstream and the reduction of NO_(x) will occur more efficientlywith a more uniform mixture of reductant and NO_(x) entering thecatalyst. In some instances, this can result in a shortened length forthe exhaust aftertreatment system by reducing the length of adecomposition reactor where the reductant and exhaust gas mix and/or thelength of the catalyst.

As described herein, a controller can utilize vehicle properties (e.g.,a vehicle speed, a vehicle tire pressure, a vehicle inclination angle, avehicle drive gear selection, a vehicle mass, a vehicle weight, avehicle trailer weight, or a vehicle air line pressure), engineproperties (e.g., an engine fuel flow rate, an engine air flow rate, anengine boost pressure, an engine intake pressure, an engine load, anengine rotational speed, an engine cylinder temperature, an enginecylinder pressure, or an engine fuel pressure), exhaust properties,and/or reductant properties (e.g., flow rates, momentum, evaporation,temperatures, a reductant air supply pressure, a reductant air supplyflow rate, a reductant spray cone angle, and/or densities) with systemand component characteristics (e.g., doser nozzle geometry, such asorifice diameter) to determine a desired reductant injection droplet andspray momentum for an ideal in-exhaust spray distribution and spatialplacement. The controller can then control a reductant injection dropletsize and/or spray momentum for an in-exhaust spray distribution andspatial placement, such as by adjusting a reductant injection supplypressure, adjusting a dosing frequency, or doser nozzle geometry. Thus,the controller can control either single droplets or a spray cloud(e.g., the mathematical integration of all the single droplets). Theforegoing are illustrative examples of control actions to deliver adesired momentum/distribution, but other possible mechanisms to delivera desired momentum/distribution may be utilized, either in addition orin lieu of the foregoing. By controlling a reductant injection dropletmomentum for a desired in-exhaust spray distribution and spatialplacement, an optimization of emissions treatment efficiencies (e.g. ahigh distribution and/or deNO_(x) percentage) and minimization ofinefficiencies (e.g. impaction/impingement of reductant on an internalpipe geometry, such as walls, mixers, diffusers, flow directors, etc.)can be achieved.

FIG. 2 depicts a graphical plot 200 of a flight path 210 of dosedreductant within a uniform exhaust vector flow. The dosed reductant isprovided at a static, preset reductant droplet momentum from a doser.That is, regardless of the exhaust flow conditions, the dosed reductantis provided at a preset reductant droplet momentum based on a reductantinjection supply pressure, a reductant injection frequency, and a staticdoser nozzle geometry. As shown in the plot 200, the flight path 210 foran example droplet or set of droplets is linear in location, therebyresulting in substantially all of the dosed reductant being located atthe injected location. Such a static, preset reductant injectionmomentum remains at the dosed location in the exhaust flow and thenrequires either turbulation of the exhaust flow and/or a length ofdecomposition reactor pipe to disperse into the exhaust flow from thedosed location.

FIG. 3 depicts a graphical plot 300 showing a droplet particle sizedistribution as a function of reductant injection supply pressure. Asshown in the plot 300, the reductant droplet diameter is larger at lowinjection supply pressures, such as 35 to 50 micrometers (μm) atreductant injection supply pressures of 6 to 8 bar. The reductantdroplet diameter decreases as the reductant injection supply pressureincreases, such as less than 25 μm at reductant injection pressuresabove 13 bar.

FIG. 4 depicts several flight paths 410, 420, 430, 440 for reductantdroplets injected into an exhaust pipe at different reductant dropletdiameters with a constant reductant injection supply pressure orinjection velocity into a constant uniform exhaust flow field. A firstflight path 410 corresponds to a droplet having a diameter of 20 μm andshows that the droplet has minimal penetration into the exhaust flow. Asecond flight path 420 corresponds to a droplet having a diameter of 40μm and shows that the droplet has an improved further penetration intothe exhaust flow. A third flight path 430 corresponds to a droplethaving a diameter of 80 μm and shows that the droplet has furtherimproved penetration into the exhaust flow. A fourth flight path 440corresponds to a droplet having a diameter of 100 μm and shows that thedroplet has still a further improved penetration into the exhaust flow.As shown by the flight paths 410, 420, 430, 440 for reductant dropletsof varying diameters, the depth of penetration into an exhaust flowincreases with increased reductant droplet diameter for reductantinjected at the same injection supply pressure or injection velocity.

At low temperatures, decomposition time for reductant droplets increasesdue to chemical kinetic limitations. Thus, at lower temperatures,ensuring small reductant droplet diameters improves quick decompositionwithin the exhaust flow. In addition, when reductant droplets are small,the depth of penetration is limited, which may be preferred at idle ornear idle conditions when exhaust flow velocity is low, and thus drag isalso low.

FIG. 5 depicts several flight paths 510, 520, 530, 540 for a 40 μmdiameter reductant droplet injected into an exhaust pipe at differentreductant injection velocities (which is directly based on the reductantinjection supply pressure) with a constant reductant droplet diameterinto a constant uniform exhaust flow field. A first flight path 510corresponds to a droplet having an injection velocity of 20 meters persecond (m/s) and shows that the droplet has minimal penetration into theexhaust flow. A second flight path 520 corresponds to a droplet havingan injection velocity of 40 m/s and shows that the droplet has animproved further penetration into the exhaust flow. A third flight path530 corresponds to a droplet having an injection velocity of 60 m/s andshows that the droplet has further improved penetration into the exhaustflow. A fourth flight path 540 corresponds to a droplet having aninjection velocity of 120 m/s and shows that the droplet has still afurther improved penetration into the exhaust flow. As shown by theflight paths 510, 520, 530, 540 for reductant droplets of varyinginjection velocities, which directly correlate to the injection supplypressure, the depth of penetration into an exhaust flow increases withincreased injection supply pressure for reductant injected at the samereductant droplet diameter.

FIG. 6 a graphical plot 600 of a flight path 610 of dosed reductantwithin a uniform exhaust vector flow. The dosed reductant is provided atvarying reductant droplet momentums from a doser such that reductantdroplets take different paths within the exhaust flow to provide alarger distribution of reductant droplets compared to the flight path210 shown in FIG. 2 . That is, based on the exhaust flow conditions, thedosed reductant is provided at different reductant droplet momentumsbased on changes to a reductant injection supply pressure, a reductantinjection frequency, and/or a variable doser nozzle geometry. As shownin the plot 600, the flight path 610 for the injected dropletspenetrates to multiple locations in the exhaust flow, thereby resultingin a better in-exhaust distribution. Such a varying reductant injectionmomentums can dose reductant to multiple locations in the exhaust flow,which may reduce or eliminate the need for exhaust flow turbulationand/or reduction to the length of a decomposition reactor pipe from thedosed location to a face of a downstream catalyst.

The injected reductant momentum can be determined based on solving thefollowing equations:

$\begin{matrix}{{\frac{P_{1}}{\rho_{1}} + {\frac{1}{2}*V_{1}^{2}} + {g*Z_{1}}} = {\frac{P_{2}}{\rho_{2}} + {\frac{1}{2}*V_{2}^{2}} + {g*Z_{2}}}} & {{Eq}.1}\end{matrix}$ $\begin{matrix}{P_{1} = {f\left( {T_{1},d_{1}} \right)}} & {{Eq}.2}\end{matrix}$ $\begin{matrix}{\rho_{1} = {f\left( T_{1} \right)}} & {{Eq}.3}\end{matrix}$ $\begin{matrix}{V_{1} = {f\left( P_{1} \right)}} & {{Eq}.4}\end{matrix}$ $\begin{matrix}{d_{1} = {f\left( T_{1} \right)}} & {{Eq}.5}\end{matrix}$ $\begin{matrix}{P_{2} = {f\left( {T_{e},P_{e},V_{e}} \right)}} & {{Eq}.6}\end{matrix}$ $\begin{matrix}{\rho_{2} = {f\left( T_{e} \right)}} & {{Eq}.7}\end{matrix}$ $\begin{matrix}{V_{2} = {f\left( {P_{e},P_{2},V_{e}} \right)}} & {{Eq}.8}\end{matrix}$ $\begin{matrix}{d_{2} = {f\left( {T_{e},T_{1}} \right)}} & {{Eq}.9}\end{matrix}$

where:

-   -   T₁ Temperature of fluid upstream of orifice, [° C.]    -   ρ₁ Density of fluid upstream of the orifice, [kg/m³]    -   ρ₂ Density of fluid at the orifice, [kg/m³]    -   T_(e) Exhaust gas temperature, [° C.]    -   ρ_(e) Density of exhaust gas, [kg/m³]    -   P_(e) Exhaust gas pressure, [Pa]    -   V_(e) Exhaust gas velocity, [m/s]

FIG. 7 depicts an implementation of a process 700 for developing acontrol model for droplet control in an exhaust system. The controlmodel may be an empirical model, analytical model, or a physics basedmodel. The process 700 includes identifying an exhaust system platformand setting up a Latin hypercube study for droplet control. Theidentification of an exhaust system platform may be a particularconfiguration for an exhaust system. The Latin hypercube study is basedon geometrical data for the exhaust system platform and ranges forvariable exhaust and reductant properties. The ranges for exhaustproperties may include exhaust gas density, exhaust pressure, exhaustflow velocity, exhaust mass flow, exhaust temperature, exhaustvorticity, etc. The ranges for reductant properties may includereductant velocity based on reductant injection supply pressure,reductant droplet diameter, variable nozzle geometries, etc. The process700 further includes performing the Latin hypercube study on dropletcontrol using a set of one or more ordinary, partial, linear, ornonlinear differential equations to solve for resulting flowdistributions and/or other values for each value of the ranges ofexhaust properties and reductant properties. The Latin hypercube studyis performed to compute parameters of the empirical model or physicsbased model for an exhaust system platform using a range of values forexhaust properties and reductant properties The process 700 alsoincludes determining if the results of the Latin hypercube study beingabove a predetermined clustering density and performing a regressionanalysis to develop a control model for the controller of an enginehaving the exhaust system platform. The process 700 further includesdetermining if the model substantially conforms or agrees with the setof one or more ordinary, partial, linear, or nonlinear differentialequation solution, such as by inputting test values into the controlmodel and the ordinary differential equation solution and comparing anerror between the output values to a predetermined threshold, such as±5%. If the test values are within the predetermined error threshold,then the control model may be implemented into the controller of theengine.

FIG. 8 depicts an implementation of a process 800 for implementing thedeveloped control model of FIG. 7 for droplet control in an exhaustsystem. The process 800 includes accessing current vehicle properties(e.g., a vehicle speed, a vehicle tire pressure, a vehicle inclinationangle, a vehicle drive gear selection, a vehicle mass, a vehicle weight,a vehicle trailer weight, or a vehicle air line pressure), engineproperties (e.g., an engine fuel flow rate, an engine air flow rate, anengine boost pressure, an engine intake pressure, an engine load, anengine rotational speed, an engine cylinder temperature, an enginecylinder pressure, or an engine fuel pressure), exhaust gas properties,and/or reductant liquid properties (e.g., flow rates, momentum,evaporation, temperatures, a reductant air supply pressure, a reductantair supply flow rate, a reductant spray cone angle, and/or densities),and a target spatial reductant distribution. In some implementations,the target spatial reductant distribution is a uniform distribution ofreductant in the exhaust system. In other implementations, the targetspatial reductant distribution may be an asymmetrical or othernon-uniform reductant distribution, such as an asymmetrical distributionof reductant for an elbow of a pipe. A reductant distribution can referto a particle spectral density, which is a statistical measure of thepercentage of droplets of a certain diameter in a spray cloud.

The current vehicle condition properties may be based on sensed orvirtual parameter values indicative of one or more properties of avehicle speed, a vehicle tire pressure, a vehicle inclination angle, avehicle drive gear selection, a vehicle mass, a vehicle weight, avehicle trailer weight, or a vehicle air line pressure. The currentengine condition properties may be based on sensed or virtual parametervalues indicative of one or more properties of an engine fuel flow rate,an engine air flow rate, an engine boost pressure, an engine intakepressure, an engine load, an engine rotational speed, an engine cylindertemperature, an engine cylinder pressure, or an engine fuel pressure.The current exhaust gas properties may be based on sensed or virtualparameter values indicative of one or more properties of the exhaust gasflow through the exhaust system, such as an exhaust temperature, anexhaust density, an exhaust pressure, an exhaust flow velocity, anexhaust mass flow, an exhaust vorticity, etc. The current reductantliquid properties may be based on sensed or virtual values indicative ofone or more properties of the reductant, such as a reductanttemperature, reductant velocity based on injection supply pressure,reductant density, injection frequency, nozzle geometry, a reductant airsupply pressure, a reductant air supply flow rate, a reductant spraycone angle, etc. The target spatial reductant distribution may be basedon a preset reductant distribution and/or scalar value representative ofa reductant distribution, such as a distribution of 0.9 indicative ofreductant being dispersed through 90% of the exhaust flow.

The process 800 includes a real-time calculation of the reductant spraymomentum needed to meet the target spatial reductant distribution. Insome instances, a reductant droplet momentum, a reductant droplet spraymomentum, or a reductant momentum vector may be used either in additionor in lieu of the reductant spray momentum. The reductant spray momentumis based on an injection supply pressure, a dosing frequency, a nozzlegeometry, etc. The reductant spray momentum may be calculated using thecontrol model from FIG. 7 . A control parameter or set of controlparameters (e.g., a commanded pump flow value, a nozzle orificediameter, an injection frequency, etc.) is determined to meet the targetspatial reductant distribution. In some implementations, the controlparameter or set of control parameters are based on a determinedinjection supply pressure, dosing frequency, and nozzle geometry. Insome implementations, the nozzle orifice size, nozzle interior angle,nozzle length or other physical properties of the doser nozzle geometrymay be adjusted responsive to a control parameter. The process 800includes comparing the determined control parameter value or set ofcontrol parameter values to current control parameter values and eithermaintaining the current control parameter values if the difference iszero or below a predetermine threshold (e.g., below 0.5% difference). Ifthe determined control parameter values are different or above thepredetermined threshold, then the process 800 includes determining ifthe determined control parameter values are within a range of parametervalues for the exhaust system. For instance, a determined pump speedvalue may be outside the range of pump speeds capable of the pump of theexhaust system. In such an instance, the current control parameter valueis set to the maximum or minimum value. If the determined controlparameter values are within the range of parameter values for theexhaust system, then the current control parameter values are updated tothe determined control parameter values. Thus, the process 800 permitsthe controller to control the different components of the reductantsupply system and/or reductant dosing system to vary control parametersto obtain a desired reductant spray momentum to meet the target spatialreductant distribution.

In some implementations, the control parameter values may be valuesstored in a look-up table that the controller determines based on theaccessed current exhaust gas properties, current reductant liquidproperties, and target spatial reductant distribution. In otherimplementations, the control parameter values may be determined based onreal-time solving of a set of one or more ordinary, partial, linear, ornonlinear differential equations by the controller to provide real-timecontrol using the current exhaust gas properties, reductant liquidproperties, and target spatial reductant distribution.

In some implementations, the reductant supply system may have one ormore characteristics that may be modified (e.g., pump speed, valveposition, etc.) with a constant characteristic reductant injectionsystem such that only the characteristics of the reductant supply systemmay be modified. In other implementations, the reductant injectionsystem may have one or more characteristics that may be modified (e.g.,air supply pressure, nozzle geometry, dosing frequency, etc.) with aconstant characteristic reductant supply system such that only thecharacteristics of the reductant injection system may be modified. Infurther implementations, both the reductant injection system and thereductant supply system may have one or more characteristics that may bemodified (e.g., pump speed, valve position, air supply pressure, nozzlegeometry, dosing frequency, etc.).

For instance, at low exhaust flow rates, a lower momentum is needed toensure a target spray distribution in the exhaust flow. As momentum is afunction of both mass and velocity, the system can modify either or bothof these injection characteristics to deliver the dosed reductant at thetarget spray distribution. In one implementation, the system couldmodify the operating pressure of the reductant supply system whilemaintaining constant characteristics for the reductant injection system.In another implementation, the system could modify the operating orificediameter of the reductant injection system while maintaining constantcharacteristics for the reductant supply system. In a furtherimplementation, the system could modify the operating pressure ofreductant supply system while modifying the operating orifice diameterof the reductant injection system. Each of the foregoing control actionsreduce the droplet momentum to achieve the target spray distribution.

By adapting the reductant supply and/or injection systems to control thereductant spray momentum, the system can decrease deposit formation andincrease reductant distribution for high performance of NO_(x) reductionSCR systems.

The term “controller” encompasses all kinds of apparatus, devices, andmachines for processing data, including by way of example a programmableprocessor, a computer, a system on a chip, or multiple ones, a portionof a programmed processor, or combinations of the foregoing. Theapparatus can include special purpose logic circuitry, e.g., an FPGA oran ASIC. The apparatus can also include, in addition to hardware, codethat creates an execution environment for the computer program inquestion, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, across-platform runtime environment, a virtual machine, or a combinationof one or more of them. The apparatus and execution environment canrealize various different computing model infrastructures, such asdistributed computing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astandalone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub programs, or portions of code).

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of what may beclaimed, but rather as descriptions of features specific to particularimplementations. Certain features described in this specification in thecontext of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresdescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described components and systems cangenerally be integrated in a single product or packaged into multipleproducts embodied on tangible media.

As utilized herein, the terms “approximately,” “about,” “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims. Additionally, it is noted that limitations in theclaims should not be interpreted as constituting “means plus function”limitations under the United States patent laws in the event that theterm “means” is not used therein.

The terms “coupled” and the like as used herein mean the joining of twocomponents directly or indirectly to one another. Such joining may bestationary (e.g., permanent) or moveable (e.g., removable orreleasable). Such joining may be achieved with the two components or thetwo components and any additional intermediate components beingintegrally formed as a single unitary body with one another or with thetwo components or the two components and any additional intermediatecomponents being attached to one another.

The terms “fluidly coupled,” “in fluid communication,” and the like asused herein mean the two components or objects have a pathway formedbetween the two components or objects in which a fluid, such as water,air, gaseous reductant, gaseous ammonia, etc., may flow, either with orwithout intervening components or objects. Examples of fluid couplingsor configurations for enabling fluid communication may include piping,channels, or any other suitable components for enabling the flow of afluid from one component or object to another.

It is important to note that the construction and arrangement of thesystem shown in the various exemplary implementations is illustrativeonly and not restrictive in character. All changes and modificationsthat come within the spirit and/or scope of the describedimplementations are desired to be protected. It should be understoodthat some features may not be necessary and implementations lacking thevarious features may be contemplated as within the scope of theapplication, the scope being defined by the claims that follow. Inreading the claims, it is intended that when words such as “a,” “an,”“at least one,” or “at least one portion” are used there is no intentionto limit the claim to only one item unless specifically stated to thecontrary in the claim. When the language “at least a portion” and/or “aportion” is used the item can include a portion and/or the entire itemunless specifically stated to the contrary.

1.-20. (canceled)
 21. A system comprising: a reductant injection systemfor injecting reductant into an exhaust gas based on an injectionparameter or a supply parameter; and a controller configured to: accessa current exhaust gas condition parameter; determine one or more controlparameters based on a control model and as a function of the accessedcurrent exhaust gas condition parameter; and modify a value of theinjection parameter or the supply parameter based on the one or morecontrol parameters to control a reductant spray momentum, a reductantdroplet momentum, or a reductant momentum vector from the reductantinjection system so as to provide a target spray droplet distribution ora target spray distribution.
 22. The system of claim 21, wherein thecurrent exhaust gas condition parameter comprises at least one of anexhaust gas pressure, an exhaust gas density, an exhaust gastemperature, an exhaust gas flow velocity, an exhaust gas mass flow, oran exhaust gas vorticity.
 23. The system of claim 21, wherein thecontrol model is based on a Latin hypercube study performed to computeparameters of an empirical model for an exhaust gas system platformusing a range of values for exhaust gas properties and reductantproperties.
 24. The system of claim 21, wherein: the controller isfurther configured to access at least one of a current vehicle conditionparameter, a current engine condition parameter, or a current reductantcondition parameter; and the one or more control parameters aredetermined further based on the at least one of the current vehiclecondition parameter, the current engine condition parameter, or thecurrent reductant condition parameter.
 25. The system of claim 24,wherein: the controller is configured to access the current reductantcondition parameter; the one or more control parameters are determinedbased on the current reductant condition parameter; and the currentreductant condition parameter comprises at least one of a reductanttemperature, reductant momentum based on an injection supply pressure, areductant density, a reductant air supply pressure, a reductant airsupply flow rate, or a reductant spray cone angle.
 26. The system ofclaim 24, wherein: the controller is configured to access the currentvehicle condition parameter; the one or more control parameters aredetermined based on the current vehicle condition parameter; and thecurrent vehicle condition parameter comprises at least one of a vehiclespeed, a vehicle tire pressure, a vehicle inclination angle, a vehicledrive gear selection, a vehicle mass, a vehicle weight, a vehicletrailer weight, or a vehicle air line pressure.
 27. The system of claim26, wherein: the controller is configured to access the currentreductant condition parameter, the one or more control parameters aredetermined based on the current reductant condition parameter, and thecurrent reductant condition parameter comprises at least one of areductant temperature, reductant momentum based on an injection supplypressure, a reductant density, a reductant air supply pressure, areductant air supply flow rate, or a reductant spray cone angle.
 28. Thesystem of claim 24, wherein: the controller is configured to access thecurrent engine condition parameter, the one or more control parametersare determined based on the current engine condition parameter, and thecurrent engine condition parameter comprises at least one of an enginefuel flow rate, an engine air flow rate, an engine boost pressure, anengine intake pressure, an engine load, an engine rotational speed, anengine cylinder temperature, an engine cylinder pressure, or an enginefuel pressure.
 29. The system of claim 21, wherein the control model isan empirical model.
 30. The system of claim 21, wherein the controlmodel is a physics based model.
 31. The system of claim 30, whereinparameters of the physics based model are obtained by performing a Latinhypercube study for an exhaust gas system platform using a range ofvalues for exhaust gas properties and reductant properties.
 32. Thesystem of claim 21, wherein the controller uses at least the currentexhaust gas condition parameter to determine the reductant spraymomentum and modifies the value of the injection parameter to achievethe target spray droplet distribution or the target spray distributionfor the current exhaust gas condition parameter.
 33. A methodcomprising: accessing a current exhaust gas condition parameter;determining one or more control parameters based on a control model andas a function of the accessed current exhaust gas condition parameter;modifying a value of an injection parameter or a supply parameter basedon the one or more control parameters to control a reductant spraymomentum, a reductant droplet momentum, or a reductant momentum vectorfrom a reductant injection system so as to provide a target spraydroplet distribution or a target spray distribution; and commanding thereductant injection system to inject reductant into an exhaust gas basedon the injection parameter or a reductant supply system to supplyreductant to the reductant injection system based on the supplyparameter.
 34. The method of claim 33, wherein the current exhaust gascondition parameter comprises at least one of an exhaust gas pressure,an exhaust gas density, an exhaust gas temperature, an exhaust gas flowvelocity, an exhaust gas mass flow, or an exhaust gas vorticity.
 35. Themethod of claim 33, wherein at least the current exhaust gas conditionparameter is used to determine the reductant spray momentum and tomodify the injection parameter to achieve the target spray dropletdistribution or the target spray distribution for the current exhaustgas condition parameter.
 36. The method of claim 33, further comprisingaccessing at least one of a current vehicle condition parameter, acurrent engine condition parameter, or a current reductant conditionparameter; wherein the one or more control parameters are determinedfurther based on the at least one of the current vehicle conditionparameter, the current engine condition parameter, or the currentreductant condition parameter.
 37. The method of claim 36, furthercomprising accessing the current reductant condition parameter; whereinthe one or more control parameters are determined based on the currentreductant condition parameter, and wherein the current reductantcondition parameter comprises at least one of a reductant temperature,reductant momentum based on an injection supply pressure, a reductantdensity, a reductant air supply pressure, a reductant air supply flowrate, or a reductant spray cone angle.
 38. The method of claim 36,further comprising accessing the current vehicle condition parameter;wherein the one or more control parameters are determined based on thecurrent vehicle condition parameter, and the current vehicle conditionparameter comprises at least one of a vehicle speed, a vehicle tirepressure, a vehicle inclination angle, a vehicle drive gear selection, avehicle mass, a vehicle weight, a vehicle trailer weight, or a vehicleair line pressure.
 39. The method of claim 38, further comprisingaccessing the current reductant condition parameter; wherein the one ormore control parameters are determined based on the current reductantcondition parameter, and wherein the current reductant conditionparameter comprises at least one of a reductant temperature, reductantmomentum based on an injection supply pressure, a reductant density, areductant air supply pressure, a reductant air supply flow rate, or areductant spray cone angle.
 40. The method of claim 36, furthercomprising accessing the current engine condition parameter; wherein theone or more control parameters are determined based on the currentengine condition parameter, and the current engine condition parametercomprises at least one of an engine fuel flow rate, an engine air flowrate, an engine boost pressure, an engine intake pressure, an engineload, an engine rotational speed, an engine cylinder temperature, anengine cylinder pressure, or an engine fuel pressure.